Measurement of flow velocities of a medium using a temperature sensitive electrical resistor which is cooled by the medium which flows around it in dependence of the flow velocity thereof, thereby changing the resistance, are known.
These known devices all comprise three discrete elements: the sensor wire, an amplifier for amplifying the measuring signal obtained as a result of the change of the resistivity of the measuring resistor, and a signal display device. As a result such devices occupy a lot of space and are not cheap to produce, as each sensing resistor must be connected to its own amplifier. An arrangement in which many sensors are used, for instance when measuring flow velocities on many points on a model of an aeroplane, such as done at windtunnel tests becomes very complicated and expensive.